Airfoils used in the field of aviation fall generally into two categories: fixed-wing, when its application emphasizes horizontal displacement of the aircraft, and rotary-wing when its usage requires more emphasis on vertical displacement. In subsonic flight, both of said categories produce lift generated by the shape of the wing combined with the movement of gaseous fluid over and around the wing. In particular, the leading edge of the wing is shaped to produce a flow of fluid at a higher velocity over the top of the wing when compared to the velocity below the bottom of the wing. Due to the Bernoulli Effect, the pressure sensed at the wing surfaces are reduced, but because the fluid velocity at the top wing surface is greater than that at the lower, a lower pressure will be sensed at the top. This differential pressure represents the lift used to produce flight. Fixed-wing aircraft rely upon forward motion of the aircraft to produce the fluid flow required to generate lift. Rotary-wing aircraft are configured to rotate the wings around a central mast thereby forcing the flow of fluid over and around the wings as they rotate. In both a fixed-wing and a rotary-wing configuration, the motion of the wing through air produces drag, the aerodynamic force that opposes the wings motion through the air. The greater the lift required, the greater the velocity of air required over the wing, and thereby, the greater the drag produced. With powered flight, in both fixed-wing and rotary-wing configurations, drag consumes a significant portion of power generated by the engine.
The lift generated by the flow of fluid over and around the wing depends upon the maintenance of a boundary layer, which in turn is dependent upon the configuration of the leading edge of the wing and by the angle of attack. As the boundary layer separates from the wing, the amount of lift is decreased. This flow separation can be caused by increasing the angle-of-attach, (i.e. the angle of the wing section relative to the direction of flight) or by changes in the geometry of the leading-edge, such as the accumulation of ice on the leading-edge. As the fluid flow approaches complete separation from the wing surface, a stall in induced where insufficient lift is produced to maintain flight. (According to the Federal Aviation Administration of the U.S. Government, loss of control, mainly stalls, account for most General Aviation accidents).
The present invention specifically addresses, in scenarios that emphasize horizontal displacement (i.e. fixed-wing airfoils) and in those that emphasize vertical displacement (i.e. rotary-wing airfoils), the effects of drag and of flow/boundary layer separation, said separation occurring either at high angle of attack and/or because of distortion of the geometry of the leading-edge.